1. Field of the Invention
The present invention relates to the field of hip positioning, especially for analyzing risk of fracture, evaluating bone gain or loss, and effect of fracture treatment. More specifically, this invention relates to hip positioning of individuals prior to using Dual X-ray Absorptiometry (DXA).
2. Description of the Related Art
Bone loss almost always follows menopause. As individuals age, they lose bone substance and become increasingly susceptible to fractures. Elderly individuals suffer an increased incidence of broken bones, particularly in the wrist, shoulder, spine, and hip. Of these breaks, hip fractures are often the most serious to the patient as well as to society.
A hip fracture in an elderly individual usually requires an operation to stabilize the break and improve the prognosis. Even after an operation, up to 20% of fracture patients still die, while the remainder often require chronic hospital or nursing home care. It costs an estimated ten billion dollars annually to care for those with broken hips caused by loss of bone or osteoporosis. As our elderly population continues to grow, the financial drain will increase each year.
Current technology allows doctors to predict the risk of hip fracture by determining the amount of bone remaining in the specific area of the proximal femur. Most doctors use DXA scanning to measure a bone mineral density (BMD) and bone mineral concentration (BMC) of several areas of the hip. Usually, a patient lies on a scanning table with only the patient's foot fixed to a positioning device. The positioning device provides support for adducting the patient's foot 20 degrees. Adduction refers to rotating an individual's limb inward toward the median axis of the body, and abduction refers to rotating an individual's limb outward from the median axis of the body.
Current devices do not attempt to fix the position of the hip and knee in any particular location, however. This is unfortunate because the position of the hip, knee, and foot greatly affect the femoral neck's aspect to a DXA scanning beam. As a result, the BMD and BMC measurements often vary between scans. Successive hip scans of the same patient may vary by 3-4%, which is up to three times greater than a scanning machine's margin of error. Variations this large hamper doctors and researchers attempting to assess BMD gains or losses in the femoral neck.
To quantify these positioning variations, consider that a post-menopausal woman typically loses only approximately 1% of BMD per year and current osteoporosis treatment only increases BMD 0-2%. Hip positioning variations, however, are up to three times as large as BMD changes to be measured. This forces doctors and researchers to wait several months before being able to confidently notice a clear trend of BMD loss or gain from data scattered by positioning variations.
The magnitude of positioning variations also requires researchers to increase the number of patients studied to achieve statistically significant results. In all cases, the size of the positioning variations results in increased costs and delayed assessments.
In light of the foregoing, there is a need for a hip positioning apparatus which improves the precision of hip positioning to present the same femoral neck aspect for successive DXA scans. Such a hip positioning apparatus will reduce the errors caused by position variations and thus improve the accuracy of predicting hip fracture and accessing fracture treatment.
There is also a need for a hip positioning device that is lightweight, simple to install, easily adjusted to individual anatomical differences, and easy for the scanning technician to use.
Additional advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out in the appended claims.